Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

New Customer with Compatibility Issues of Cooling/Heating Units

I've got a store owner that has a Goodman Heat Pump outdoor unit with an indoor unit which is a Trane Propane furnace with a coooling coil. Have little service history from previous techs and store owner said units were originally installed that way. From the 3 or so blown 3amp fuses found by the indoor unit the units have run together for the dozen years that store has been open but lately been having issues during both cooling and heat seasons. The store owner wants to keep existing units for the time being...I am wondering what best appraoch would be? Could I wire the Propane furnace on its own thermostat for Heating only to get him by this winter or is there a way to wire these units on a heat pump thermostat without blowing fuses. ill have more precise details about the units when I go back. I just have never seen a gas furnace/cooling coil connected to a Heat Pump outdoor unit...

If it has been there a while, it probably has a dual fuel kit mounted in the furnace with an external thermostat in the condensing unit. Its my understanding that this old technology. I agree with cbowling79 that a thermostat can now do the job. I believe I would verify the existing components before installing the new thermostat.

Vision Pro 8000

Use a Vision pro 8000 very Easy to wire them for a dual fuel purpose with a outdoor stat you can lock out the heat pump on outdoor air temp and run propane only I have this set up in my house

Yeah that sounds good, Vision Pro 8000. I was only there briefly and when restarting the gas furnace before it retripped the control board fuse it appeared the Chronotherm digital thermostat indicated Heat Mode and not Emergency Heat (or Auxillary Heat) when the furnace fired. To my limited Heat Pump servicework that means the thermostat is wired wrong. The storeowner told me that during last summer the heatpump needed work and was told that the coil contactor of the condensing unit was frying the control board fuse in the indoor unit. Ill just trace down the condensing unit wiring and disconnect its wiring so I can still fire up the furnace until I can get the Vision Pro.
Most of my background is with Heating and Central AC in the Northeast where it was too cold for Heatpumps. Thanks for your input!

Dual fuel is the way to go with heat pumps. The most expensive heat is pure resistive, second is gas heating, and the cheapest is movement of heat i.e. heat pump. In my opinion the gas option is best when the temperature goes below the critical point.

Make sure there isn't a "Fossil Fuel Kit" on it that's just been wired wrong. If the contactor coil is drawing high amps and blowing the fuse, replace the contactor or at the very least the contactor coil. Goodman had a circuit board kit that would make fossil fuel furnaces compatible with their heat pumps, but you may also have a kit installed when the furnace was set. Sounds like someone has installed the Goodman unit after the original outdoor unit failed, and never hooked up the system properly,,,,,by the way, is the cooling coil upstream of the furnace(in the return air duct), or downstream of the furnace (in the discharge duct)?
Generally, Heat pumps installed on Fossil fuel furnaces are controlled so that the furnace and the heat pump operate in conjunction with each other, so when the furnace is running, the heat pump is locked out, and when the heat pump is running, the furnace is disabled. In Heat pump systems with electric heat, the two sources run consecutively, with heat pump running on 1st stage, and the electric heat coming on in a call from the thermostat for 2nd stage heat. Both sources of heat can operate at the same time.

One way to outthink people is to make them think you think. They'll think you're not really thinking what you're trying to get them to think you think...........

The storeowner says everything is orignal installs. There are two Trane propane furnaces installed up in attic space with cooling coils downstream of furnaces. Both outdoor units are Goodman heat pumps. Will the Vision Pro 8000 tstats solve the issues if they dont have fossil fuel kits? I havent checked yet so far on fossil fuel kits but I will see if they have them. It appears both units have been having trouble with the Goodman units. The one had three or so blown fuses next to the unit from past service and the other Trane unit has had a board replaced on it as well, a shipping box with the old board is sitting on top of it.The only info I had on service was that the owner thought that the contacor was replaced over summer.

How far away are the condensing units from the furnaces? If the transformers are in the furnaces, you may have too much low voltage drop to run everything. Make sure you have a load on the contactor before checking voltage across the contactor coil. This may seem obvious, but I learned you dont know much until the device has a load on it, the hard way, like most lessons!

If you determine the blown fuses are being blown due to a problem in the remote heat pump I would disconnect the low voltage wiring from it and simple wire a heating only stat to the Trane Propane Furnace. This will create an opportunity in the spring for a remote condenser replacement. I assume the air to air heat pump repair would exceed the value of the unit....

The vision pros will work to control the system on its own with no other kits needed if you want to lock the heat pumps out on outdoor temp you will need a outdoor sensor and two extra wires outside to hook it up I shut mine off at 30 and run my propane